Randomized Ballot Order Can Increase Invalid Votes: Evidence from Australia

Randomized ballot order of electoral candidates prevents unfair advantages for candidates with favorable positions on a ballot, but it also places additional cognitive strain on voters who need to search for their preferred candidates without clues. This strain could increase voters' probability of making errors. Using more than 68,000 polling-place level data from Australian House of Representatives elections, we show that the stronger the candidate at the top of a ballot, the smaller the percentage of informal (i.e., invalid and unrecorded) votes. This is because, for a larger number of voters, the most favorable candidate appears at the easiest-to-find position. The magnitude of this effect is particularly large when the number of candidates is large. Our finding implies that designing a ballot to maximize fairness among candidates could bring about an unintended consequence that is inconsistent with another important normative principle -- maximized (valid) voter participation.